One of the things that I recommend to DBAs is that as they write code to solve problems, they write some sort of check to catch future potential occurrences of the issue. For example, I worked with a product years ago that had an identity column as an int, but this product scanned thousands of our systems every 5 minutes, logging each scan. We found that after 8-12 months, we'd run out of identity ranges. 

While we considered changing to a bigint, this was a third party product and they did not want to allow us to alter the schema. Since there were only a few million rows in the table at any one time, we decided to write a check that would alert us when the table came close to running out of integer values. A DBA could then easily reseed the identity property to prevent issues.

Across my career I've found many other instances where we could write checks to find issues before users were impacted. At SQLServerCentral we have checks looking for discrepancies in points awarded, in incorrect status values, and more. These often don't impact the users of the site, but they are alerts that let administrators know about potential problems before they become issues.

This week I'm wondering:

What types of common issues have you found that could be valuable as checks for other DBAs?

Perhaps looking for delays in replication or Service Broker? Jobs that never stop or never execute for some reason? Memory or space alerts? Do you look for localsystem as a service account? Let us know what checks you've written, or which ones you wish were available for you to download and use on your systems.